sqlite3 package document mistake

[seeker-Liu]

BPO	42624
Nosy	@terryjreedy, @berkerpeksag, @erlend-aasland, @seeker-Liu

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-12-12.08:47:49.871>
labels = ['type-bug', '3.9', 'docs']
title = 'sqlite3 package document mistake'
updated_at = <Date 2021-02-12.12:00:09.639>
user = 'https://github.com/seeker-Liu'

bugs.python.org fields:

activity = <Date 2021-02-12.12:00:09.639>
actor = 'erlendaasland'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-12-12.08:47:49.871>
creator = 'seeker-Liu'
dependencies = []
files = []
hgrepos = []
issue_num = 42624
keywords = []
message_count = 7.0
messages = ['382904', '383329', '383367', '386859', '386860', '386861', '386862']
nosy_count = 6.0
nosy_names = ['terry.reedy', 'ghaering', 'docs@python', 'berker.peksag', 'erlendaasland', 'seeker-Liu']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42624'
versions = ['Python 3.9']

[seeker-Liu]

In the document about sqlite3 package, it was suggested that when users are trying to create a table already exists, sqlite3.ProgrammingError is going to be thrown. However, the actual exception thrown is sqlite3.OperationalError, which is inconsistent with the document.

Doc: https://docs.python.org/3/library/sqlite3.html#exceptions

[terryjreedy]

The doc is the same in 3.10.

What OS and exact Python release? Can you post minimal code that verifies your claim? (Someone what have to verify with 3.10 also.)

This would strike me as an error in the code. We can fix 'wrong Exception' in the next release. I am not sure whether we would do so in a current release.

[seeker-Liu]

Python 3.9.1 (default, Dec 11 2020, 14:32:07) 
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sqlite3
>>> conn = sqlite3.connect("test.db")
>>> conn.execute("CREATE TABLE test (id INTEGER, str TEXT);")
<sqlite3.Cursor object at 0x7ff99f2df3b0>
>>> conn.execute("CREATE TABLE test (id INTEGER, str TEXT);")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
sqlite3.OperationalError: table test already exists
>>> 

I think the reproduction is way too easy and has nothing special so I didn't include one at the very beginning. That's a simple reproduction on interactive console.

[erlend-aasland]

Exception originates from _pysqlite_seterror() in Modules/_sqlite/util.c, line 64:
https://github.com/python/cpython/blob/master/Modules/_sqlite/util.c#L64

Error code 1 (SQLITE_ERROR, https://sqlite.org/rescode.html#error) is a generic sqlite3 error. Changing the default sqlite3 exception for this error code may not be what we want.

Anyway, we should clean up the exceptions emitted in the sqlite3 module. There are other inconsistencies apart from this.

[erlend-aasland]

Ref. gh-68327 (bpo-24139)

[erlend-aasland]

... and also gh-60583 (bpo-16379)

[erlend-aasland]

*error handling => exception emitted

[erlend-aasland]

The sqlite3 exception docs section has been rewritten in main (Python 3.12) by gh-27645, so this is considered fixed in main. I decided not to backport the docs update, because there's been a lot of work related to improving the exceptions raised by the sqlite3 extension module, and only parts of that work exists in 3.11, and even less in 3.10.

[erlend-aasland]

We could backport gh-27645 to 3.11, and possibly also 3.10, but it will be hairy.

[erlend-aasland]

I backported gh-27645 to 3.11 and 3.10:

• [3.11] gh-89018: Improve documentation of sqlite3 exceptions (GH-27645) #93836
• [3.10] gh-89018: Improve documentation of sqlite3 exceptions (GH-27645) #93838

I consider this issue resolved. If there are further inconsistencies, please open a new issue.